SNC1D – Grade 9 IB Science – Exam Notes

Thanks, Faizah!

Equations

Density D = mV

 

D – density

m – mass

V – volume

Work W = Fd

 

W – work (J – joules)

F – force (N – newton)

d – distance (m – metres)

Current Electricity W = VIt

 

W – electrical energy (J – joules)

V – voltage

I – current (A – amperes)

t – time (s – seconds)

Power P = Wt

 

P – power (W – watts)

W – work (J – joules)

t – time (s – seconds)

Ohm’s Law V = IR

I = VR

R = VI

 

V – electric potential (V – voltage)

I – electric current (A – amperes)

R – resistance (- Ohms)

Mark and Recapture (eco) first capturedpopulation total=second capture markedsecond capture total

 

Unit 1 Sustainable Ecosystems

Chapter 1 – Nutrient Cycles and Energy Flow

 

Ecosystem – all the interacting parts of a biological community and its environment.

Sustainable Ecosystem – an ecosystem that is capable of with standing pressure and giving support to a variety of organisms.

Biotic – The living parts of an ecosystem

Abiotic – The nonliving parts of an ecosystem.

 

Biotic Interactions

  • Symbiosis
    • The interaction between members of two different species that live together in close association
  • Predation
    • Occurs when one organism consumes another organism for food. The organism consumed is called the prey and the organism that eats the prey is called the predator.
  • Competition
    • Occurs when two or more organisms compete for the same resources such as food, in the same location in the same time.

 

Abiotic Characteristics

  • Water
    • All organisms need water to survive.
    • Both natural processes and human activities can affect the amount and quality of water in an ecosystem.
  • Oxygen
    • Oxygen is an essential for life.
    • Because of human activities, oxygen levels can get so low that many organisms cannot survive.
  • Light
    • Plants and other organisms need light to go through photosynthesis.
    • The amount of light each ecosystem receives can vary.
  • Nutrients
    • All organisms need nutrients to grow.
    • Nutrient levels in an ecosystem can become unbalanced due to human activities.
  • Soil
    • Soil provides nutrients for plants and a habitat for many micro organisms.
    • Top layers of soil, which contain the most nutrients can be washed away if there is heavy rain or if too many trees have been cut down.

 

Earth’s Spheres

Lithosphere – The hard part of the Earth’s surface.

Hydrosphere – All the water found on Earth, including lakes, oceans, and ground.

Atmosphere – The layer of gases above Earth’s surface.

Biosphere – The regions of Earth where living organisms exist.

 

Nutrient Cycles

Nutrient – A chemical that is essential to living things and is cycles through ecosystems.

 

Water Cycle – Evaporation ⇒ Condensation ⇒ Precipitation, Ice + Snow ⇒ Run Off + Groundwater + Ocean Water

Carbon Cycle

  • Carbon Dioxide in air is absorbed by plants to make sugars.
  • Organisms break down sugars made by plants to obtain energy. CO2 is released as waste.
  • Burning fossil fuels and wood releases CO2 into atmosphere.
  • When organisms die, carbon containing molecules become part of the soil. Decomposers break down organic matter, releasing CO2 in the air.
  • The remains of organic matter may gradually process into energy rich carbon compounds such as coal and fossil fuels.

Nitrogen Cycle

  • Nitrogen from the atmosphere is converted into ammonium (NH4) by soil bacteria.
  • Ammonium is converted into nitrate (NO2) by other types of soil bacteria.
  • Plants absorb both forms of nitrogen through their roots.
  • Nitrogen is passed from one level of the food chain to the next.
  • Fertilizers containing ammonium and nitrates enter aquatic and terrestrial ecosystems.
  • Bacteria in land and water convert nitrogen back into nitrogen gas, returning to the atmosphere.
  • Nitrogen can also return to the atmosphere as ammonia (NH3) during burning of fossil fuels and volcanic eruptions.

Phosphorus Cycle

  • Exists only in lithosphere.
  • Stored in rocks and sediments, when broken down, forms into phosphate (PO4).
  • Phosphate rocks are also drilled by humans which make fertilizers and detergents.
  • When phosphate is in the soil, it is absorbed by the roots of plants and moves through the biosphere.
  • Decomposers break down dead organic matter which releases phosphate back into soil

Eutrophication – A process in which nutrient levels in aquatic ecosystems increase, leading to the increase in the populations of primary producers.

Photosynthesis – A process that changes solar energy into chemical energy.

  • 6CO2 + 6H2O ⇒ light energy ⇒ C6H12O6 + 6O2

Trophic Levels – A category of organisms that is defined by how the organisms gain their energy.

Biomass – The total mass of living organisms in a defined group or area.

Trophic Efficiency – A measure of the amount of energy or biomass transferred from one trophic level to the next higher trophic level.

Bioaccumulation – A process in which materials, especially toxins, are ingested by an organism at a rate greater than they are eliminated.

Cellular Respiration – A process that releases energy from organic molecules, especially carbohydrates, in the presence of oxygen.

Fermentation – A process that releases energy from organic molecules, especially carbohydrates, in the absence of oxygen.

Greenhouse Gases  – Atmospheric gases that prevent heat from leaving the atmosphere, thus increasing the temperature of the atmosphere.

Greenhouse Effect – The warming of Earth as a result of greenhouse gases, which trap some of the energy that would otherwise leave.

 

Reducing Carbon Dioxide in the Atmosphere

Kyoto Protocol – Is an international agreement to reduce greenhouse gas emissions, which was signed by over 180n countries, by planting trees in non-forested areas.

Protecting Existing Forests – Forests protected from logging, mining, and oil and natural gas exploration

Recycling Programs – Reduces CO2 emissions because less energy is needed to make things out of recycled materials than from new materials.

 

Chapter 2 – Populations and Sustainable Ecosystems

Population – All the individuals of a species that occupy a particular geographic area at certain a time.

Exponential Growth – Accelerating growth that produces a J – shaped curve when the population is graphed against time.

Limiting Factors – A factor that limits the growth, distribution, or amount of a population in an ecosystem.

Carrying Capacity – The size of a population that can be supported indefinitely by the available resources and services of an ecosystem.

Equilibrium – The balance between opposing forces.

Ecological Niche – The way that an organism occupies a position in an ecosystem, including all the necessary biotic and abiotic factors.

Bog – A type of wetland in which is acidic and low in nutrients.

Mutualism – A symbiotic relationship between two species in which both species benefit from the relationship.

Parasite – An organism whose niche is dependant on a close association with a larger host organism.

Sustainable Use – Use that does not lead to the long-term depletion of a resource or affect the

diversity of the ecosystem from which the resource is obtained.

Ecological Footprint – A measure of the impact of an individual or a population on the environment in terms of energy consumption, land use and waste products.

Sustainability – Use of Earth’s resources, including land and water, at levels that can continue forever.

Biodiversity – The number and variety of life forms including species found within a specific region as well as the number and variety of ecosystems within and beyond that region.

 

Methods of Measuring Biodiversity

  • Canopy Fogging
    • Is an effective way of collecting information about the biodiversity of insects. A low dose of insecticide is sprayed up into the top of a tree. When the insects fall, they are collected on a large screen, shaped like a funnel. This helps scientists learn more about the life cycle of these insects.
  • Quadrat Sampling
    • A known square area is marked using a pre-made square of plastic, or stakes and string. Different species and their numbers within the quadrat are counted. Counting is repeated many times in different places throughout the habitat to get an accurate representation of biodiversity.
  • Transect Sampling
    • Done using a transect line, a rope or measuring tape that has been marked at set intervals, such as every metre. The line is unrolled within the habitat. At every interval, the type and number of species along the line are recorded.
  • Netting Fine
    • Used to capture bird, bats and fish. Once captured, an organism is identified. In addition, it may be measured, blood may be taken for genetic analysis, and it may be tagged.

 

Chapter 3 – Biodiversity

Biodiversity Hotspot – A place where there is an exceptionally large number of species in a relatively small area

Community – All the populations of the different species that interact in a specific area or ecosystem

Dominant Species – Species that are so abundant that they have the biggest biomass of any community Member Keystone Species – A species that can greatly affect population numbers and the health of an ecosystem.

Captive Breeding – The breeding of rare or endangered wildlife in controlled settings to increase the population size.

Ecosystem Engineer – A species that causes such dramatic changes to landscapes that it creates a new ecosystem.

Succession – The series of changes in an ecosystem that occurs over time, following a disturbance.

Habitat Loss – The destruction of habitats, which usually results from human activities

Deforestation – The practice of clearing forests for logging or other human uses, and never replanting them.

Alien Species – A species that is accidentally or deliberately introduced into a new location.

Invasive Species – A species that can take over the habitat of native species or invade their bodies.

Overexploitation – The use or extraction of a resource until it is depleted.

Extinction – The death of all the individuals of a species.

Stewardship – The active assumption of responsibility for the welfare of the environment.

Restoration Ecology – The renewal of degraded or destroyed ecosystems through active human intervention.

Reforestation – The regrowth of a forest, either through natural processes or through the planting of seeds or trees in an area where a forest was cut down.

Biocontrol – The use of a species to control the population growth or spread of an undesirable species.

Bioremediation – The use of living organisms to clean up contaminated areas naturally.

Bioaugmentation – The use of organisms to add essential nutrients to depleted soils.

 

Unit 2 Atoms, Elements, and Compounds

Chapter 4 – Properties of Elements and Compounds

Matter – Anything that has mass and occupies space.

Pure Substance – Matter that contains only one kind of particle.

Mixture – Matter that contains more than one kind of particle.

Element – A pure substance that cannot be broken down into simpler parts by chemical methods.

Compound – A pure substance made of two or more different elements that are chemically combined.

 

Separating Mixtures

  • Filtering
    • Can be used to separate solids from liquids or gases.
  • Distillation
    • Can be used to separate liquids in a mixture, based on boiling point.
  • Magnetism
    • Will attract iron and steel objects and leave other objects behind.

Physical Property – A characteristic of a substance that can be observed and measured without changing the identity of the substance.

 

Qualitative Physical Properties Property

⇒ colour, odour, state, texture, lustre, malleability

Melting Point – The temperature at which a solid turns into a liquid.

Boiling Point – The temperature at which a liquid turns into a gas.

Solubility – A measure of the ability of a substance to dissolve in another substance.

Density =  mass / volume or D = m / V

Chemical Property – The ability of a substance to change (react) and form new substances.

Quantitative Physical Properties Property

⇒ viscosity, melting point, solubility, hardness, conductivity, density

Examples of Reactivities Description

  • `Reactivity with Water
    • Calcium carbide is a compound that reacts with water to generate acetylene gas. The acetylene gas is combustible, which makes it useful for generating light.
  • Reactivity with Oxygen
    • Aluminum metal is very reactive with oxygen. The reaction causes a layer of aluminum oxide to form on the surface of the aluminum, which protects the metal from weathering. This helps to keep aluminum objects that are always exposed to the environment from corroding.
  • Reactivity with Acids
    • Baking soda, is a compound that reacts with acids to create carbon dioxide gas. Many recipes for baked goods use baking soda because the bubbles of carbon dioxide that form help to make batter and dough rise.
  • Reactivity with Another Pure Substance
    • Knowing how pure substances react with each other provides the basis that enables chemists to develop new products.

Combustibility – The ability of a substance to burn in air.

Stability – The ability of a substance to remain unchanged.

Toxicity – The ability of a substance to cause harmful effects in plants and animals.

 

Chapter 5 – Understanding the Properties of Elements

Atom – The smallest particle of an element that retains the identity of the element.

Electron – A negatively charged particle within the atom.

Subatomic Particle – A particle that is smaller than the atom.

Proton – A positively charged particle that is part of every atomic nucleus.

Neutron – An uncharged particle that is part of almost every atomic nucleus.

 

Evolution of the Atom

Democritus

  • Greek philosopher, father of modern atomic thought.
  • Proposed that matter could NOT be divided into smaller pieces forever.
  • Claimed that matter was made of small, hard particles that he called “atomos”

John Dalton

  • Created the very first atomic theory.
  • Viewed atoms as tiny, solid balls.
  • Theory consisted of four statements
    • 1. Atoms are tiny, indivisible particles.
    • 2. Atoms of one element are all the same.
    • 3. Atoms of different elements are different.
    • 4. Compounds form by combining atoms.

J.J. Thomson

  • Discovered electrons.
  • Proposed the existence of  protons
  • His atomic model was known as the “raisin bun model”
  • First scientist to show that the atom was made of even smaller things.

Ernest Rutherford

  • Discovered protons and the nucleus.
  • Showed that atoms have (+) particles in the center, and are mostly empty space.
  • He called the center of atoms the nucleus.
  • Gold Foil Experiment
    • Most alpha particles went right through,  some particles were deflected
    • Discovered the atom is mostly empty space.
    • Some particles deflected and others even bounced back
    • The atom had a very dense (+) center.

Niels Bohr

  • Improved on Rutherford’s model.
  • Every atom has a specific number of electron shells.
  • Proposed that electrons move around the nucleus in specific layers, or shells.

James Chadwick

  • Chadwick discovered neutrons.
  • He called these particles neutrons.
  • He discovered particles with no charge (neutrons), also found in the nucleus.

 

Atomic Number – The number of protons in the nucleus of an atom.

Mass Number – The sum of the number of protons and the number of neutrons in the nucleus of an atom.

Isotope – One of two or more forms of an element that have the same number of protons but a different number of neutrons.

Atomic Mass – The average mass of the naturally occurring isotopes of an element .

Periodic Table – A system for organizing the elements into columns and rows, so that elements with similar properties are in the same column.

 

Physical Properties of Metals and Nonmetals

Metals ⇒ solid (mercury is a liquid), shiny, good conductors of heat and electricity, malleable and ductile.

Non-metals ⇒ some gases and some solids (except bromine, which is a liquid), not very shiny, poor conductors of heat and electricity, brittle and not ductile.

 

Period – A horizontal row of elements in the periodic table.

Group – A vertical column of elements in the periodic table.

Valence Electron – An electron in the outermost occupied energy level of an atom.

 

Chapter 6 – Understanding Properties of Compounds

Ion – A positively or negatively charged atom or molecule.

Chemical Bond – A chemical link between two atoms, which holds the atoms together

Ionic Bond – A chemical bond that forms between oppositely charged ions.

Ionic Compound – A compound made of oppositely charged ions.

How To Name Ionic Compounds ⇒ name of metal + (name of nonmetal + ide)

 

Physical States of Ionic Compounds

⇒ Exists in a solid arrangement called a crystal lattice.

⇒ Most soluble in water.

⇒ Good electrical conductors.

Molecular Compound – A compound formed when atoms of two or more different elements share electrons.

Covalent Bond – A chemical bond in which one or more pairs of electrons are shared by two atoms.

Molecule – The smallest discrete particle of a pure substance, which has one or more shared pairs of electrons.

How To Name Molecular Compounds ⇒ (prefix + name of first nonmetal) +  (prefix + name of second nonmetal)

Properties of Molecular Compounds

⇒ Weak force of attraction between particles = low melting and boiling point and soft

⇒ Poor conductors of electricity and heat

⇒ Many cannot dissolve as well as ionic compounds

 

Unit 3 The Study of the Universe

Chapter 7 – The Night Sky

Calendar – A way of showing days, organized into a schedule of larger units of time, such as weeks, months, seasons, or years; usually a table or a chart.

Celestial Object – Any object that exists in space, such as a planet, a star, or the Moon.

Astronomer – A scientist who studies astronomy, which is the study of the night sky.

Revolution – The time it takes for an object to orbit another object; Earth’s revolution around the Sun is 365.24 days.

Rotation – The turning of an object around an imaginary axis running through it.

Constellation – A group of stars that seem to form a distinctive pattern in the sky.

Light-Year – The distance that light travels in one year, about 9.5 × 1012 km.

Apparent Magnitude – The brightness of a star as seen from Earth.

  • Smaller groups of stars that form patterns within a constellation are called asterisms, from the Greek word aster, meaning star.

 

Latitude – The location above or below the equator.

 

  • Constellations are groupings of stars that form distinctive patterns. The stars in these groupings appear to be close to each other, but they are not.
  • A star’s apparent magnitude is its brightness as seen from Earth.
  • The Big Dipper is an asterism, which is a smaller grouping of stars within a constellation.
  • Earth’s rotational axis points to Polaris, the North Star. For thousands of years, travellers have used Polaris and the constellations to navigate.
  • Different cultures have different interpretations of the night sky.
  • A light-year is the distance that light travels in one year.

 

Tides – The rising and falling of ocean waters as a result of the Moon’s gravity and Earth’s gravity.

Ellipse – A curve that is generally referred to as an oval or the shape of an egg.

Phases of the Moon – The monthly progression of changes in the appearance of the Moon, which result from different portions of the Moon’s sunlit side being visible from Earth.

Eclipse – The phenomenon in which one celestial object moves directly in front of another celestial object.

Lunar Eclipse – The phenomenon in which the full Moon passes into Earth’s shadow.

Solar Eclipse – The phenomenon in which the shadow of the Moon falls on Earth’s surface.

Gravitational Force – The force of attraction between all masses in the universe.

 

  • The tilt of Earth’s axis, combined with Earth’s motion around the Sun, gives rise to the seasons.
  • We see different phases of the Moon, depending on where the Moon is in relation to Earth.
  • During a lunar eclipse, the Moon passes through Earth’s shadow.
  • During a solar eclipse, the Moon passes in front of the Sun.
  • The tides are a result of the difference between the force of gravity on the side of Earth nearest the Moon and the force of gravity on the side of Earth farthest from the Moon.

 

Planet – An object that orbits one or more stars (and is not a star itself), is spherical, and does not share its orbit with another object.

Solar System – A group of planets that circle one or more stars.

 

  • The planets Mercury, Venus, Earth, and Mars are called the inner/ terrestrial (Earth-like) planets.
  • Jupiter, Saturn, Uranus, and Neptune are outer planets or gas giants.

 

Retrograde Motion – The movement of an object in the sky, usually a planet, from east to west, rather than in its normal motion from west to east.

Astronomical Unit – The average distance between Earth and the Sun, about 150 × 106 km.

Orbital Radius – The average distance between the Sun and an object that is orbiting the Sun.

 

  • Two models of the solar system are the geocentric model and the heliocentric model.
  • The planets share many similar characteristics, but they also have many differences.
  • The inner, or terrestrial, planets are rocky and small. The outer planets, or gas giants, are made of gases and are huge.
  • The astronomical unit is defined as the average distance between Earth and the Sun.

 

Comet – An object composed of rocky material, ice, and gas; comes from the Kuiper Belt and Oort Cloud.

 

  • Objects that circle the Sun beyond the orbit of Neptune are called trans-Neptunian objects, located in the Kuiper Belt

 

Asteroid – A small object that ranges in size from a tiny speck, like a grain of sand, to 500 km wide; most asteroids originate in the asteroid belt between Mars and Jupiter.

Meteoroid – A piece of rock moving through space.

Meteor – A meteoroid that hits Earth’s atmosphere and burns up.

Meteorite – A meteoroid that is large enough to pass through Earth’s atmosphere and reach the ground, without being totally burned up.

 

  • In addition to planets, the solar system contains many different objects, such as dwarf planets, asteroids, comets, and meteors.
  • There is a very real danger that an asteroid or a large meteor will hit Earth again.
  • The Canadian Space Agency and Canadian businesses are building a satellite that will help to detect near-Earth objects that could be harmful if they hit Earth.

 

Chapter 8 – Exploring Our Stellar Neighbourhood

Electromagnetic Radiation – Radiation consisting of electromagnetic waves that travel at the speed of light (such as visible light, radio waves, and X rays).

Refracting Telescope – A telescope that uses a lens to collect the light from an object.

Reflecting Telescope – A telescope that uses a mirror to collect the light from an object.

 

Disadvantages and Advantages of Placing Telescopes in Space

Advantages

  • They are above Earth’s atmosphere, so they can detect parts of the electromagnetic spectrum that do not reach Earth’s surface.
  • They can take long exposures of certain parts of the sky without being affected by daylight and bad weather. This allows the telescopes to detect faint astronomical objects not otherwise detectable on the ground.

Disadvantages

  • Launching into space is very expensive.
  • Are subjected to extremes of hot and cold. Such extremes cause the metals used in the instruments to expand and contract. Over time, the materials weaken. Once in space, very difficult or impossible to repair and upgrade.
  • Without a solid base,  they are difficult to point accurately and to keep pointing in any direction. Earth-based telescopes are anchored to the ground.
  • Compared with Earth-based telescopes, the working lives of space telescopes are very short, sometimes lasting only a few years.

 

Satellite – A human-made object or vehicle that orbits Earth, the Moon, or other celestial bodies; also, a celestial body that orbits another of larger size

Ethics – The set of moral principles and values that guide a person’s activities and help him or her decide what is right and what is wrong.

Solar Nebula – Theory the theory that describes how stars and planets form from contracting, spinning disks of gas and dust.

Star – A celestial body made of hot gases, mainly hydrogen and some helium.

Nebula – A vast cloud of gas and dust, which may be the birthplace of stars and planets.

Protostar – Hot, condensed object at the centre of a nebula.

Nuclear Fusion – The process of energy production in which hydrogen nuclei combine to form helium nuclei.

Photosphere – The surface layer of the Sun.

Sunspot – An area of strong magnetic fields on the photosphere.

Solar Wind – A stream of fast moving charged particles ejected by the Sun into the solar system.

 

  • The solar nebula theory says that the Sun and the solar system formed from a spinning, contracting disk of gas and dust particles.
  • Evidence supporting the solar nebula theory consists of heavily cratered objects, most planets rotating in about the same direction, most planets revolving in the same direction and in about the same plane, and the existence of other planets around other stars.
  • The Sun’s energy source is hydrogen. It converts matter into energy through nuclear fusion.
  • Sunspots can produce solar flares, which send gigantic beams of charged particles into space.

 

Luminosity – A star’s total energy output per second; its power in joules per second (J/s).

Absolute Magnitude – The magnitude of a star that we would observe if the star were placed 32.6 light-years from Earth.

Spectroscope – An optical instrument that produces a spectrum from a narrow beam of light, and usually projects the spectrum onto a photographic plate or a digital detector.

Spectral Lines – Certain specific wavelengths within a spectrum characterized by lines; spectral lines identify specific chemical elements.

Hertzsprung–Russell – Diagram a graph that compares the properties of stars.

Main Sequence – A narrow band of stars on the H-R diagram that runs diagonally from the upper left (bright, hot stars) to the lower right (dim, cool stars); about 90 percent of stars, including the Sun, are in the main sequence.

White Dwarf – A small, dim, hot star.

Supernova – A massive explosion in which the entire outer portion of a star is blown off.

Neutron Star – A star so dense that only neutrons can exist in the core.

  • The earth’s northern hemisphere is tilted towards the sun in summer and away from it in the winter

 

Chapter 9 – The Mysterious Universe

Milky Way – The galaxy that includes the solar system; appears as a hazy white band in the night sky.

Galaxy – A huge collection of stars, planets, gas, and dust that is held together by gravity.

 

Shapes of Galaxies

  • Spiral Galaxy
    • Looks like a pinwheel when viewed from above.
    • Looks like a plate with a bulge in the middle when viewed from the side.
  • Eliptical Galaxy
    • Range in shape from a perfect sphere to a ellipse.
    • Contain some of the oldest stars in the universe.
    • It is believed that well over half of the galaxies and the largest in the universe are Eliptical.
  • Irregular Galaxy
    • Do not have a regular shape.
    • Made of newly forming stars and old stars.

 

Star Cluster  – A collection of stars held together by gravity.

Open Cluster – A collection of 50 to 1000 stars; open clusters appear along the mainband of the Milky Way.

Globular Cluster  – A collection of 100000 to a million stars, arranged in a distinctive speherical shape; globular clusters appear around the centre of the Milky Way.

Local Group – The small group of galaxies that include the Milky Way.

Supercluster – A gigantic cluster of 4 to 25 clusters of galaxies, which is hundreds of millions of light-years in size.

Cosmology – The study of the universe.

Doppler Effect – The change in frequency of a light source due to its motion relative to an observer; also, the change in pitch of a sound due to the motion of the source relative to an observer.

Redshift –  The effect in which objects moving away from an observer have their wavelengths lengthened, toward the red end of the visible spectrum.

Blueshift –  The effect in which objects moving toward an observer have their wavelengths shortened, toward the blue end of the visible spectrum.

Big Bang – The event that may have triggered the expansion of the universe 14 billion years ago.

Cosmic Microwave Background – The radiation left over from the big bang which fills the universe.

Dark Matter – The most abundant form of matter in the universe, invisible to telescopes.

Dark Energy – A form of energy that makes up nearly three quarters of the universe; has the effect of increasing the expansion of the universe.

 

Unit 4 The Characteristics of Electricity

Static Charges & Energy

Electricity – a form of energy that results from the interaction of charged particles, such as electrons or protons

Current Electricity – the flow of electrical charges

Static Charge (static electricity) – an electric charge that tends to stay on the surface of an object, rather than flowing away quickly

Charging by Friction – a process in which objects made from different materials rub against each other, producing a net static charge on each (net charge = overall charge)

Charging by Contact – generating a charge on a neutral object by touching it with a charged object

Electric Field – a property of the space around a charged object,, where the effect of its charge can be felt by other objects

Induced Charge Separation – the movement of electrons in a substance caused by the electric field of a nearby charged object, without the direct contact between the substance and the object

Electroscope – a device for detecting the presence of an electric charge

Law of Electric Charges: – laws that describe how two objects interact electrically when one or both are charged

  1. Like charges repel
  2. Opposite charges attract
  3. Charged and neutral objects attract each other

General Other Rules:

  1. Protons and neutrons never move or leave the atom. They remain part of the nucleus always.
  2. Electrons move and can be transferred from atom to atom.

 

Electrostatic Series

Insulator – a material in which electrons cannot move easily from one atom to another (e.g. rubber)

Conductor – a material in which electrons can move easily between atoms (e.g. copper wire)

Semiconductor – a material in which electrons can move fairly well between atoms (e.g. humans)

Ground – an object that can supply, take, or store a very large number of electrons

Electrostatic Series – a list of materials that have been arranged according to their ability to hold on to electrons. Below is an electrostatic series of some common materials

(weak – strong hold on electrons) Glass, Human Hair, Nylon, Wool, Fur, Silk, Cotton, Lucite (a clear plastic), rubber balloon, Polyester, Foam, Grocery Bags (low-density polyethylene), Ebonite

When one is rubbed with another, the weaker substance will lose its electrons and become positive. The stronger substance would then gain the electrons and become negative.

General Things to Note:

  1. Neutral: # of protons = # of electrons
  2. Positive: lose electrons (more protons than electrons)
  3. Negative: gain electrons (more electrons than protons)
  4. Ebonite rubbed with fur = Ebonite is negative, fur is positive
  5. Glass rod rubbed with silk = Glass is positive, silk is negative

 

Electric Circuits

Electric Circuit: – closed path along which electrons can flow – has an energy source – electrons flow from one terminal (-ve) of energy source to another terminal (+ve)

Components:  

Switch – a control device that allows the path to be broken, disrupting the flow of electrons (e.g. light switch)

– allows the circuit to be closed

Open Electric Circuit – a circuit with a break in the flow of electrons

How Electrons Move: – when a conductor disconnects from an energy source, its electrons move randomly – the energy source, its electrons move randomly – the energy source produces an excess of electrons at the negative terminal, producing an electric field in the conductor -electric field causes the electrons to move in one direction through the wire – electrons flow through the path of least resistance

Measuring Electric Charge:

Coulomb (C) – bundle of electrons used to measure the charge – # of electrons passing a point – 1C – charge of 6.25 x 1018 electrons

Electric Current: – rate of movement of electric charge (flow of electrons)

– measured in Amperes (A) → 1A = 1C of charge passing in 1s – measured using an ammeter, connected in series

  1. i) Cells

Voltaic Cell – a source of electric current energy generated by chemical reactions between two different metals, separated by a conducting solution

Battery – a connection of 2+ cells

Electrode – metal terminal in a cell or battery

Electrolyte – a solution or a paste that conducts charge

Dry Cell – a cell that contains an electrolyte that is a paste

Wet Cell – a cell that contains a liquid electrolyte

Primary Cell – cell that can only be used once

Secondary Cell – cell that can only be used once

Fuel Cell – a cell that generates electricity through the chemical reactions of fuel that is stored outside the cell

Solar Cell – a cell that converts sunlight into electrical energy

Load – a device that transforms electrical energy into heat, motion, sound or light (e.g. toaster, radio, etc.)

Using Electric Circuit Symbol

  1. ii) Series & Parallel

Series: (figure 5) – 1 path for electrons

– when there is a break in the series, all loads don’t receive the charge – in series, identical bulbs may not have the same intensity – is used up quickly – ”AND” -stronger intensities of energy, but rate changes per load

Parallel: (figure 6) – 2+ paths of electrons – when 1 path is off, other parts of the circuit may still be on – if light bulbs are identical in different branches, they have the same intensities – ”OR” -lasts longer

– has consistent power

 

Loads in Series                                    Loads in Parallel

IT = I1 = I2 = I3                                    It = I1 + I2 + I3

VT = V1 + V2 + V3                   VT = V1 = V2 = V3

RT = R1 + R2 + R3                               RT > R1, RT < R2                     ← OR              1RT = 1R1 + 1R2 + 1R3

  1. iv) Electrical Resistance

Electron Flow in Conductors:

  1. in a conductor not connected to an energy source, electrons move randomly
  2. in a conductor connected to a source of electrical energy, the electrons move in one direction through it

Electrical Resistance (R) – a conductor’s ability to resist the flow of electrons to some extent (resistance would generally refer to impede the flow of particles in a material) – causes a loss of electric potential

Potential Difference (V drop/electric potential) – difference in the amount of electrical potential after electrons have flowed through the conductor – measured in voltage (V)

Electric Current (I) – flow of electrical charges – measured in amperage (A)

Resistor

  1. decreases electrical current through a component by a set amount
  2. used to safely supply a load with needed Volts
  3. reduces current
  4. made of alloys

Ohm’s Law – the potential difference between two points on a conductor is proportional to the current flowing

V = I R                         I = V / R                                   R = V / I

  • higher resistance = lower electrical current

Factors that Affect Resistance:

  1. type of material (e.g. Copper vs Iron)
  2. Resistance of wires in direct relation to their length → 2x length = 2 x R
  3. Diameter: D+ = R-
  4. Temperature: ℃+ = R+

Short Circuit – +ve & -ve terminals of cell may touch a metal key and complete the circuit with no electrical load to use up battery energy. Key and cell may heat up enough to combust

 

Electricity in the Home

Direct Current (D/C): – the current type from a cell – electrons go in 1 direction

Alternating Current (A/C): – the current type from wall outlets – electrons move different ways

Distribution of Energy:

  1. Generator – converts a source of energy (wind, water, solar, chemical, etc.) into electrical energy
  2. Transformer – changes voltage up to 500’000
  3. Transmission Lines – carries electrical energy long distances at high voltages
  4. Substation – reduce voltage for local use
  5. Distribution Transformer – reduce voltage for local use
    1. Electric Meter – when electricity arrives to your home, it passes this to measure the amount of energy used
    2. Distribution Panel (older homes) – consists of circuit breaker & fuses – electric supply is connected to the distribution panel – enters through 2 live wires, and 1 neutral ground wire – light & wall outlets in home operate at 120 W – circuit breaker is connected in series with the distribution panel
  • wall outlets & lights are connected in parallel
  1. i) Electrical Safety in the Home

Circuit Breaker: – limits the amount of current to a set value – prevents overheating in wires which leads to  electrical fires – placed in series with electrical meter and other breakers – when current exceeds limit, breaker changes shape and opens the circuit, stopping the current flow

Fuse: – function same as circuit breaker – metal conductor melts at a certain current amount, which opens the circuit, stopping the current flow

Ground Fault Circuit Interrupter (GFCI): – used instead of wall outlet when it’s found 2 metres near water

– prevents current from flowing through water – detects if there is a difference in current (if it’s out of the circuit)

– built in circuit breaker

Wall Outlet & Plugs: – prevent shock from faulty appliances – round plug connects to metal frame of appliance

Surge Protector: – prevents circuit damage during power surges (that can be caused by lightning) – resistance builds in the surge protector when the current exceeds the set limit

Power Bar & Switch: – all connected appliances can be turned off with a single switch – parallel outlets – switch is in series with wall outlet

ii)) Sources of Electrical Energy

  • 89% of Canada’s energy is non-renewable (highest abundance – lowest abundance → oil, natural gas, and coal are our three major fossil fuels.) They make up 80% of our non-renewable resources
  • 11% is renewable energy (e.g. from running water)
  • multiple complete energy conversions are required to produce/ convert energy

Non-Renewable Sources

  • fossil fuel generating:

1) burn fossil fuel to heat up water for steam

2) high pressure turns turbines (converts to mechanical energy)

3) turbine turns electromagnetic generator and produces electricity

  • waste energy (usually) = thermal energy

iii) Energy Efficiency

  • comparison of energy used to produce, and amount of useful energy produced
  • 20-26% of fuel’s energy is converted to electrical energy (nuclear, petroleum, natural gas, coal, advanced natural gas turbine)

What to consider when buying electrical appliances:

  • price – cost of operating the device over time – durability – device’s power usage

Appliances & Typical Power Rating (kW):

  • Clock = 0.0050 – Clothes Dryer = 5.0 – Dishwasher = -1.8 – Toaster = 1.1 – Computer w/ monitor & printer = 0.2
  • *power depends on setting that the appliance is in

Energuide & Energy Star Labels

  • in Canada, household appliances must be sold with Energuide label
  • label announces amount of energy used per year, and shows how the appliance model compares to others in its class

Energy Star Label

  • Energy Star helps us save money and protect the environment w/ efficient products and practices
  • proves that the appliance meets the minimum level of efficiency
  • 20-30% less energy used than federally required

Time of Use Pricing

  • price varies with different time of the day/ day of the week
  • off-peak, mid-peak, and on-peak times
  • summer vs winter (solar power)
  • night vs day (less light)

Phantom Load

  • electricity consumed by an appliance that is off
  • it seems as though the appliance is off, but it’s actually on stand-by mode
  • TV, clock displays